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The Bubble Machine

by Dom Ruggeri

July 2004:

At one time good formulating techniques could render metal working fluids foam free.  Of course those were the days when automobiles were built of all metal and a gallon of premium fuel sold for 35 cents per gallon (Ancient History).  Today customers’ requirements are such that a coolant must last at least a year, and run trouble free with minimal care.  This requires using some very unique additives; additives that will cause foam. 

Back in the early eighties I was working for a small formulating house.  Foam was always an issue.  I was asked to develop a cleaner that would remove oily soil at a concentration of 3 percent.  Not the most difficult assignment, especially when the washer temperature was 150 degrees F.  My plan was to saponify the soil and for foam, control a surfactant with a cloud point between 100 and 120 degrees F.  I submitted the sample and it was approved.  All was going well. 

About 3 months later, we received a complaint that the cleaner was foaming out of the tank.  As always, we checked the retain sample and there was no problem.  All quality checks were fine.  All the salesman knew was that the cleaner was foaming.  My manager, then a good formulator, told the salesman to investigate this incident more completely.  This he did.  What we found was that a new engineer had turned off the heat in a cost cutting measure.  Well little wonder there was foam all over the place.  The cleaner was designed to run at 150 degrees F, not ambient temperature.  So much for product design.

My last article discussed defoamers; this offering will discuss antifoam agents.  We have all seen this at one time or another: Defoamer/Antifoam or my personal favorite Antifoam/Defoamer.  Slick marketing you betcha.  Someone is trying to convince us, the formulating community, that a product can do both jobs well.  In my many years of formulating I have never found a product that can not only prevent foam but also kill foam in a system.  I am not saying an antifoam will not kill foam in a foamy system.  It will.  But, it will not do it as effectively as a particle type defoamer. 

Antifoams are formulated into neat metal working fluids (normally at 0.1 to 0.3 percent).  When the metalworking fluid is diluted, normally 95 percent water to 5 percent fluid, the antifoam goes to infinite dilution.  The antifoam moiety then comes to the surface of the dilution and prevents the foam from building up.  In an ideal situation the antifoam creates a steady state where as fast as the foam is formed it is broken. 

Now, what if you have a central system where you are hip deep in foam outside the tank?  Is this a time to panic? Well that depends if the salesman is on site or not.  Either way I would follow this procedure to bring the foam under control.

Step 1:

Using a particle type defoamer on the clean side of the central system, add one quart of defoamer per thousand gallons of coolant.  The standard recommendation is one pint per thousand gallons of coolant however; this recommendation is for a system that has foam but still in control.  When the system is out of control you must kill that foam as quickly as you can but remember that you can overdose, so one quart should get the system back in control quickly.  You can always add more defoamer, but if you overdose the system you can’t take it out and you may even stabilize the foam.  This stabilization would be caused by the surfactant package in the defoamer.

Step 2:

When you begin to see surface foam on the clean side of the tank, add the antifoam.  The recommendation here is four ounces per thousand gallons of coolant.  This level will bring you to the 0.3 percent level in the neat coolant this should prevent the foam from returning for some period of time.  The reason for the return of the foam is that the antifoam will eventually be emulsified by the coolant.  This is accomplished by the action of the circulation pumps.  Another factor the filter media.  Certain types of filter media will adsorb the antifoam.  This is a systemic problem and changing the filtration media is the only solution, unless your customer is receptive to constant additions of a defoamer.

As you can see, both products function in different ways and both play a vital role in keeping a system under control.  However, no one product can do both functions well.  So in conclusion remember: a defoamer kills foam quickly while an antifoam prevents foam.  As I like to say, ‘if you don’t build it, you don’t have to break it.’

As always, should you have any questions please feel free to e-mail me in care of the magazine.  Till next month,

Good Luck